Canisters are known comprising a casing defining a chamber; and a filter housed inside the chamber and comprising bulk granules of adsorbent material, such as active carbon. More specifically, the casing defines an inlet for fuel vapour from the tank; an outlet communicating with the outside environment; and a hatch connected to the intake manifold of an internal combustion engine of the vehicle to perform cleaning cycles of the active carbon.
An active-carbon canister normally also comprises a grille cooperating with the active carbon; and elastic means interposed between a cover of the canister and the grille to compact the active carbon and prevent the granules from being damaged by stress during normal use of the vehicle, e.g. by jolting when running along uneven roads.
An adsorbing device according to the preamble of claim 1 is disclosed in U.S. Pat. No. 4,693,393.
Assembling the cover, the elastic means, and the grille, however, involve a relatively large number of operations, which increase manufacturing time.